1. Field of Invention
This invention relates to an improved cover for a food container, which cover can be easily and neatly torn off of the container as by means of half-cut score lines formed in the cover. More particularly, this invention relates to an improved container cover which will not prematurely rupture when the cover is secured to the container or roughly handled.
2. Prior Art
The packaging of foods in metal containers in which they must be heated preparatory to serving is a widespread practice. Among the foods thus packaged are raw corn kernels for making popcorn. The container includes a relatively heavy gauge aluminum foil pan and a relatively light gauge expansible aluminum foil cover sealed around its periphery to the pan. A protective paperboard cover overlays the expansible aluminum foil cover to protect the foil cover and to provide for graphics display on the top of the container.
According to U.S. Pat. No. 4,386,706, issued Jan. 7, 1983 to Kurtz, the paperboard cover can be removed from the container by means of half-cut score lines formed in the cover close to the periphery of the cover, and a tear tab formed in the cover with full-cut score lines. Removal is accomplished by lifting the tear tab and pulling upward, whereby the central portion of the cover is peeled off of the container with rupture of the cover occurring along the half-cut score lines. The peripheral margin of the cover is left attached to the container. The container also includes a wire handle which has a first portion which is secured to the periphery of the container coextensive with the periphery of the cover, and which has a second portion extending outwardly of the container to provide means for manually grasping the handle. The heavy gauge aluminum foil pan and the light gauge aluminum foil cover are sealed to each other about their coextensive edges, with the sealed edges providing a crimping skirt which is folded over the margin of the light gauge aluminum foil cover to overlie the periphery of the paperboard cover and the first portion of the wire handle. The crimping skirt is then crimped down onto the margin of the light gauge aluminum foil cover to secure the paperboard cover and the wire handle to the container.
U.S. Pat. Nos. 4,194,680, issued Mar. 25, 1980 to Scott et al; 4,194,681, issued Mar. 25, 1980 to Scott et al; 4,211,360, issued July 8, 1980 to Scott et al; U.S. Pat. No. Des. 258,350, issued Feb. 24, 1981 to Scott et al; U.S. Pat. No. Des. 259,103, issued May 5, 1981 to Scott et al; and U.S. Pat. No. Des. 260,370, issued Aug. 25, 1981 to Peterson, all disclose the general type of paperboard container cover described above.
The difficulty with these constructions is that the pull tab in the cover is full-cut scored so that the cover is weakened in the portion with the result that the inner, expandable foil could be ruptured if a sharp corner were to press down in that area. While a fold-in tab is provided to overlie the cut portion, this gives only partial protection against such inadvertent rupture.
A problem has arisen in connection with the assembly of this type of container where the paperboard cover is formed in accordance with the teachings of the prior art. When the handle and paperboard cover are secured to the container by the crimping of the compound foil skirt, the crimping forces utilized have been sufficient to produce a premature rupturing or delamination of the half-cut score lines formed in the paperboard cover to facilitate removal thereof from the container. This premature delamination, or partial delamination, is naturally undesirable as it weakens the container structure and presents an unsightly appearance.
It has been proposed to remedy this difficulty (U.S. Pat. No. 4,386,706, supra) by means of a cover which is formed with the half-cut score opening zone, as in the prior art, and is also formed with an interrupted perforate line disposed between the periphery of the cover and the half-cut score opening zone. The interrupted perforated line extends completely around the cover to surround the half-cut score opening zone outwardly of the latter. The interrupted perforated line disposed between the crimped area and the half-cut score opening zone is intended to serve to sufficiently locally increase the flexibility of the paperboard cover so that the stress forces imparted to the paperboard cover during the crimping operation are not fully transmitted to the half-cut score opening zone whereby the latter does not delaminate. Neither does the interrupted perforated line rupture during the crimping operation. Thus, the paperboard cover is secured intact to the container without premature rupture occurring in the cover.
It has been found in practice, however, that notwithstanding said perforations, and especially when the cover has a full-cut scored pull tab, the problems encountered in crimping are only partially avoided and, moreover, little if any resistance to rupture or delamination, as a result of rough handling, is provided. In addition, the cut-through openings provided by the perforations in prior art lids, which cut-through openings are not necessary according to the present invention and which are accordingly obviated by the present invention, have the disadvantage of allowing air or other material to enter into the packaging through the cut-through openings of the perforations, which may have a drying out effect and which in any event allows direct exposure of the thin protective foil to the elements.